Isomerization catalyst and process

ABSTRACT

A catalyst and process is disclosed to selectively upgrade a paraffinic feedstock to obtain an isoparaffin-rich product for blending into gasoline. The catalyst comprises a support of a tungstated oxide or hydroxide of a Group IVB (IUPAC 4) metal, a first component of at least one Group IVA (IUPAC 14) component, at least one Group VA (IUPAC 15) component or mixtures thereof, which is preferably silicon or phosphorus, and at least one platinum-group metal component which is preferably platinum.

CROSS REFERENCE TO RELATED PARAGRAPH

[0001] This application is a Division of copending application Ser. No.10/243,524, filed Sep. 13, 2002, the contents of which are herebyincorporated by reference.

FIELD OF THE INVENTION

[0002] This invention relates to an improved catalytic composite andprocess for the conversion of hydrocarbons, and more specifically forthe selective upgrading of a paraffinic feedstock by isomerization.

BACKGROUND OF THE INVENTION

[0003] The widespread removal of lead antiknock additive from gasolineand the rising fuel-quality demands of high-performanceinternal-combustion engines have compelled petroleum refiners to installnew and modified processes for increased “octane,” or knock resistance,in the gasoline pool. Refiners have relied on a variety of options toupgrade the gasoline pool, including higher-severity catalyticreforming, higher FCC (fluid catalytic cracking) gasoline octane,isomerization of light naphtha and the use of oxygenated compounds. Suchkey options as increased reforming severity and higher FCC gasolineoctane result in a higher aromatics content of the gasoline pool at theexpense of low-octane heavy paraffins.

[0004] Refiners are also faced with supplying reformulated gasoline tomeet tightened automotive emission standards. Reformulated gasolinediffers from the traditional product in having a lower vapor pressure,lower final boiling point, increased content of oxygenates, and lowercontent of olefins, benzene and aromatics. Benzene content generally isbeing restricted to 1% or lower, and is limited to 0.8% in U.S.reformulated gasoline. Gasoline aromatics content is likely to belowered, particularly as distillation end points (usually characterizedas the 90% distillation temperature) are lowered, since the high-boilingportion of the gasoline which thereby would be eliminated usually is anaromatics concentrate. Since aromatics have been the principal source ofincreased gasoline octanes during the recent lead-reduction program,severe restriction of the benzene/aromatics content and high-boilingportion will present refiners with processing problems. These problemshave been addressed through such technology as isomerization of lightnaphtha to increase its octane number, isomerization of butanes asalkylation feedstock, and generation of additional light olefins asfeedstock for alkylation and production of oxygenates using FCC anddehydrogenation. This issue often has been addressed by raising the cutpoint between light and heavy naphtha, increasing the relative quantityof naphtha to an isomerization unit.

[0005] Additionally, instead of reforming, the isomerization of longerchain hydrocarbons such as C₇ and C₈ hydrocarbons into branchedhydrocarbons of higher octane could be used to increase the octanenumber of fuels without increasing the amount of aromatics. However,many isomerization catalysts suffer significant disadvantages whenapplied to the longer chain hydrocarbons. A principal problem is thegeneration of byproducts such as cracked hydrocarbon materials. Thecracking decreases the amount of long chain paraffins available forisomerization and reduces the ultimate yield.

[0006] Several catalysts for isomerization are known, and a family oftungstated zirconia catalysts have been used. For example, U.S. Pat. No.5,510,309 B1, U.S. Pat. No. 5,780,382 B1, U.S. Pat. No. 5,854,170, andU.S. Pat. No. 6,124,232 B1 teach methods of making an acidic solidhaving a Group IVB (IUPAC 4) metal oxide modified with an oxyanion of aGroup VIB (IUPAC 6) metal such as zirconia modified with tungstate. U.S.Pat. No. 6,184,430 B1 teaches a method of cracking a feedstock bycontacting the feedstock with a metal-promoted anion modified metaloxide catalyst where the metal oxide is one or more of ZrO₂, HfO₂, TiO₂and SnO₂, the modifier is one or more of SO₄ and WO₃, and the metal isone or more of Pt, Ni, Pd, Rh, Ir, Ru, Mn, and Fe.

[0007] Others have added a noble metal such as platinum to thetungstated zirconia catalysts above, see U.S. Pat. No. 5,719,097; U.S.Pat. No. 6,080,904 B1; and U.S. Pat. No. 6,118,036 B1. A catalyst havingan oxide of a Group IVB (IUPAC 4) metal modified with an anion oroxyanion of a Group VIB (IUPAC 6) metal and a Group IB (IUPAC 11) metalor metal oxide is disclosed in U.S. Pat. No. 5,902,767. In U.S. Pat. No.5,648,589 and U.S. Pat. No. 5,422,327, a catalyst having a Group VII(IUPAC 8, 9, and 10) metal and a zirconia support impregnated withsilica and tungsten oxide and a process of isomerization using thecatalyst is disclosed. A process for forming a diesel fuel blendingcomponent uses an acidic solid catalyst having a Group IVB (IUPAC 4)metal oxide modified with an oxyanion of Group VIB (IUPAC 6) metal andiron or manganese in U.S. Pat. No. 5,780,703 B1.

[0008] U.S. Pat. No. 5,310,868 and U.S. Pat. No. 5,214,017 teachcatalyst compositions containing sulfated and calcined mixtures of (1) asupport containing an oxide or hydroxide of IUPAC 4 (Ti, Zr, Hf), (2) anoxide or hydroxide of IUPAC 6 (Cr, Mo, W); IUPAC 7 (Mn, Tc, Re), orIUPAC 8, 9, and 10 (Group VIII) metal, (3) an oxide or hydroxide ofIUPAC 11 (Cu, Ag, Au), IUPAC 12 (Zn, Cd, Hg), IUPAC 3 (Sc, Y), IUPAC 13(B. Al, Ga, In, Ti), IUPAC 14 (Ge, Sn, Pb), IUPAC 5 (V, Nb, Ta), orIUPAC 6 (Cr, Mo, W), and (4) a metal of the lanthanide series.

[0009] Applicant has developed a more effective catalyst that has provedto be surprisingly superior to those already known for the isomerizationof hydrocarbons and especially C₇ and C₈ hydrocarbons.

SUMMARY OF THE INVENTION

[0010] A purpose of the present invention is to provide an improvedcatalyst and process for hydrocarbon conversion reactions. Anotherpurpose of the present invention is to provide improved technology toupgrade naphtha to gasoline. A more specific purpose is to provide animproved catalyst and process for the isomerization of full boilingpoint range naphtha to obtain a high-octane gasoline component. Thisinvention is based on the discovery that a catalyst containing a GroupIVA component, Group VA component, or mixtures thereof plus aplatinum-group component provides superior performance and stability inthe isomerization of full boiling point range naphtha to increase itsisoparaffin content.

[0011] A broad embodiment of the present invention is directed to acatalyst comprising a tungstated support of an oxide or hydroxide of aGroup IVB (IUPAC 4) metal, preferably zirconium oxide or hydroxide, atleast a first component which is a Group IVA (IUPAC 14) component, GroupVA (IUPAC 15) component or mixtures thereof, and at least a secondcomponent being a platinum-group metal component. The first componentpreferably consists of a single Group IVA (IUPAC 14) component, Group VA(IUPAC 15) component and the second component preferably consists of asingle platinum-group metal. Preferably, the first component is siliconor phosphorus, or mixtures thereof, and the second component isplatinum. The catalyst optionally contains an inorganic-oxide binder,especially alumina.

[0012] An additional embodiment of the invention is a method ofpreparing the catalyst of the invention by tungstating the Group IVB(IUPAC 4) metal oxide or hydroxide, incorporating a first componentwhich is at least one Group IVA (IUPAC 14) component, Group VA (IUPAC15) component or any mixture thereof, and the second component which isa platinum-group metal, and preferably binding the catalyst with arefractory inorganic oxide.

[0013] In another aspect, the invention comprises convertinghydrocarbons using the catalyst of the invention. In yet anotherembodiment, the invention comprises the isomerization of isomerizablehydrocarbons using the catalyst of the invention. The hydrocarbonspreferably comprise a full boiling point range naphtha which isisomerized to increase its isoparaffin content and octane number as agasoline blending stock.

[0014] These as well as other embodiments will become apparent from thedetailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a plot of the conversion of n-heptane achieved byselected catalysts made in Example 1.

[0016]FIG. 2 is a plot of the selectivities of the catalysts of FIG. 1for n-heptane isomerization.

[0017]FIG. 3 is a plot of the selectivities of the catalysts of FIG. 1for the isomerization of n-heptane to 2,2-dimethylpentane and2,4-dimethylpentane.

[0018]FIG. 4 is a plot of the yields of the catalysts of FIG. 1 for theisomerization of n-heptane to 2,2-dimethylpentane and2,4-dimethylpentane.

[0019]FIG. 5 is a plot of the conversion of n-heptane achieved byselected catalysts made in Example 1 where silicon is a modifier.

[0020]FIG. 6 is a plot of the selectivities of the catalysts of FIG. 5for n-heptane isomerization.

[0021]FIG. 7 is a plot of the selectivities of the catalysts of FIG. 5for the isomerization of n-heptane to 2,2-dimethylpentane and2,4-dimethylpentane.

[0022]FIG. 8 is a plot of the yields of the catalysts of FIG. 5 for theisomerization of n-heptane to 2,2-dimethylpentane and2,4-dimethylpentane.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The support material of the catalyst of the present inventioncomprises an oxide or hydroxide of a Group IVB (IUPAC 4) metal, seeCotton and Wilkinson, Advanced Inorganic Chemistry, John Wiley & Sons(Fifth Edition, 1988) and including zirconium, titanium and hafnium.Preferably, the metal is selected from zirconium and titanium, withzirconium being especially preferred. The preferred zirconium oxide orhydroxide is converted via calcination to crystalline form. Tungstate iscomposited on the support material to form, it is believed without solimiting the invention, a mixture of Bronsted and Lewis acid sites. Acomponent of at least one Group IVA (IUPAC 14) component, Group VA(IUPAC 15) component, or mixtures thereof, is incorporated into thecomposite by any suitable means. A platinum-group metal component isadded to the catalytic composite by any means known in the art to effectthe catalyst of the invention, e.g., by impregnation. Optionally, thecatalyst is bound with a refractory inorganic oxide. The support,tungstate, metal components, and optional binder may be composited inany order effective to prepare a catalyst useful for the conversion ofhydrocarbons, and particularly the isomerization of hydrocarbons.

[0024] Production of the support of the present catalyst may be based ona hydroxide of a Group IVB (IUPAC 4) metal as raw material. For example,suitable zirconium hydroxide is available from MEI of Flemington, N.J.Alternatively, the hydroxide may be prepared by hydrolyzing metaloxy-anion compounds, for example ZrOCl₂, ZrO(NO₃)₂, ZrO(OH)NO₃, ZrOSO₄,TiOCl₂ and the like. Note that commercial ZrO(OH)₂ contains asignificant amount of Hf, about 1 weight percent. Zirconium alkoxidessuch as zirconyl acetate and zirconium propoxide may be used as well.The hydrolysis can be effected using a hydrolyzing agent such asammonium hydroxide, sodium hydroxide, potassium hydroxide, sodiumsulfate, (NH₄)₂HPO₄ and other such compounds known in the art. The metaloxy-anion component may in turn be prepared from available materials,for example, by treating ZrOCO₃ with nitric acid. The hydroxide aspurchased or generated by hydrolysis preferably is dried at atemperature of from about 100° C. to 300° C. to vaporize volatilecompounds.

[0025] A tungstated support is prepared by treatment with a suitabletungstating agent to form a solid strong acid. Liquid acids whosestrength is greater than sulfuric acid have been termed “superacids”. Anumber of liquid superacids are known in the literature includingsubstituted protic acids, e.g., trifluoromethyl substituted H₂SO₄,triflic acid and protic acids activated by Lewis acids (HF plus BF₃).While determination of the acid strength of liquid superacids isrelatively straightforward, the exact acid strength of a solid strongacid is difficult to directly measure with any precision because of theless defined nature of the surface state of solids relative to the fullysolvated molecules found in liquids. Accordingly, there is no generallyapplicable correlation between liquid superacids and solid strong acidssuch that if a liquid super acid is found to catalyze a reaction, thereis no corresponding solid strong acid which one can automatically chooseto carry out the same reaction. Therefore, as will be used in thisspecification, “solid strong acids” are those that have an acid strengthgreater than sulfonic acid resins such as Amberlyst®-15. Additionally,since there is disagreement in the literature whether some of thesesolid acids are “superacids” only the term solid strong acid as definedabove will be used herein. Another way to define a solid strong acid isa solid comprising of interacting protic and Lewis acid sites. Thus,solid strong acids can be a combination of a Bronsted (protonic) acidand a Lewis acid component. In other cases, the Bronsted and Lewis acidcomponents are not readily identified or present as distinct species,yet they meet the above criteria.

[0026] Tungstate ions are incorporated into a catalytic composite, forexample, by treatment with ammonium metatungstate in a concentrationusually of about 0.1 to 20 mass percent tungsten and preferably fromabout 1 to 15 mass percent tungsten. Compounds such as metatungsticacid, sodium tungstate, ammonium tungstate, ammonium paratungstate,which are capable of forming tungstate ions upon calcining, may beemployed as alternative sources. Preferably, ammonium metatungstate isemployed to provide tungstate ions and form a solid strong acidcatalyst. The tungstate content of the finished catalyst generally is inthe range of about 0.5 to 30 mass-%, and preferably is from about 1 to25 mass-% on an elemental basis. The tungstate composite is dried,preferably followed by calcination at a temperature of about 450° C. to1000° C. particularly if the tungstanation is to be followed byincorporation of the platinum-group metal.

[0027] A first component, comprising one or more of the Group IVA (IUPAC14) components, Group VA (IUPAC 15) components, or mixtures thereof, isanother essential component of the present catalyst. Included in theGroup IVA components are silicon, germanium, tin, and lead. Included inthe Group VA components are nitrogen, phosphorus, arsenic, antimony, andbismuth. Preferred elements include silicon, phosphorus, and germanium,with silicon being the most preferred. The first component may, ingeneral, be present in the catalytic composite in any catalyticallyavailable form such as the elemental metal, a compound such as theoxide, hydroxide, halide, oxyhalide, carbonate or nitrate or in chemicalcombination with one or more of the other ingredients of the catalyst.The first component is preferably an oxide, an intermetallic withplatinum, a sulfate, or in the zirconia lattice. The materials aregenerally calcined between 450° C. and 1000° C., with a preferredtemperature of about 800° C., and thus in the oxide form. Although it isnot intended to so restrict the present invention, it is believed thatbest results are obtained when the first component is present in thecomposite in a form wherein substantially all of the first component isin an oxidation state above that of the elemental state such as in theform of the oxide, oxyhalide or halide or in a mixture thereof and thesubsequently described oxidation and reduction steps that are preferablyused in the preparation of the instant catalytic composite arespecifically designed to achieve this end. The first component can beincorporated into the catalyst in any amount which is catalyticallyeffective, suitably from about 0.01 to about 10 mass-% first componentin the finished catalyst on an elemental basis. Best results usually areachieved with about 1 to about 5 mass-% of the first component,calculated on an elemental basis.

[0028] The first component is incorporated in the catalytic composite inany suitable manner known to the art, such as by coprecipitation,coextrusion with the porous carrier material, or impregnation of theporous carrier material either before, after, or simultaneously withtungstate though not necessarily with equivalent results. For ease ofoperation, it is preferred to simultaneously incorporate the firstcomponent with the tungstate. It is most preferred to incorporate theplatinum-group metal component last. As to the first component and theplatinum-group metal, the order of addition between the two does nothave a significant impact.

[0029] One method of depositing the first component involvesimpregnating the support with a solution (preferably aqueous) of adecomposable compound of the first component. By decomposable is meantthat upon heating, the compound is converted to element or oxide withthe release of byproducts. Illustrative of the decomposable compoundswithout limitation are complexes or compounds such as, nitrates,halides, sulfates, acetates, organic alkyls, hydroxides, and the likecompounds. Conditions for decomposition include temperatures rangingfrom about 200° C. to about 400° C. The first component can beimpregnated onto the carrier either prior to, simultaneously with, orafter the platinum-group metal component, although not necessarily withequivalent results. If a sequential technique is used, the composite canbe dried or dried and calcined in between impregnations.

[0030] A second component, a platinum-group metal, is an essentialingredient of the catalyst. The second component comprises at least oneof platinum, palladium, ruthenium, rhodium, iridium, or osmium; platinumis preferred, and it is especially preferred that the platinum-groupmetal consists essentially of platinum. The platinum-group metalcomponent may exist within the final catalytic composite as a compoundsuch as an oxide, sulfide, halide, oxyhalide, etc., in chemicalcombination with one or more of the other ingredients of the compositeor as the metal. Amounts in the range of from about 0.01 to about 2mass-% platinum-group metal component, on an elemental basis, areeffective, and from about 0.1 to 1 mass-% platinum-group metalcomponent, on an elemental basis, are preferred. Best results areobtained when substantially all of the platinum-group metal is presentin the elemental state.

[0031] The second component, a platinum-group metal component, isdeposited on the composite using the same means as for the firstcomponent described above. Illustrative of the decomposable compounds ofthe platinum group metals are chloroplatinic acid, ammoniumchloroplatinate, bromoplatinic acid, dinitrodiamino platinum, sodiumtetranitroplatinate, rhodium trichoride, hexa-amminerhodium chloride,rhodium carbonylchloride, sodium hexanitrorhodate, chloropalladic acid,palladium chloride, palladium nitrate, diamminepalladium hydroxide,tetraamminepalladium chloride, hexachloroiridate (IV) acid,hexachloroiridate (III) acid, ammonium hexachloroiridate (III), ammoniumaquohexachloroiridate (IV), ruthenium tetrachloride,hexachlororuthenate, hexa-ammineruthenium chloride, osmium trichlorideand ammonium osmium chloride. The second component, a platinum-groupcomponent, is deposited on the support either before, after, orsimultaneously with tungstate and/or the first component though notnecessarily with equivalent results. It is preferred that theplatinum-group component is deposited on the support either after orsimultaneously with tungstate and/or the first component.

[0032] In addition to the first and second components above, thecatalyst may optionally further include a third component of iron,cobalt, nickel, rhenium or mixtures thereof. Iron is preferred, and theiron may be present in amounts ranging from about 0.1 to about 5 mass-%on an elemental basis. The third component, such as iron, may functionto lower the amount of the first component needed in the optimalformulation. The third component may be deposited on the composite usingthe same means as for the first and second components as describedabove. When the third component is iron, suitable compounds wouldinclude iron nitrate, iron halides, iron sulfate and any other solubleiron compound.

[0033] The catalytic composite described above can be used as a powderor can be formed into any desired shapes such as pills, cakes,extrudates, powders, granules, spheres, etc., and they may be utilizedin any particular size. The composite is formed into the particularshape by means well known in the art. In making the various shapes, itmay be desirable to mix the composite with a binder. However, it must beemphasized that the catalyst may be made and successfully used without abinder. The binder, when employed, usually comprises from about 0.1 to50 mass-%, preferably from about 5 to is 20 mass-%, of the finishedcatalyst. Refractory inorganic oxide are suitable binders. Examples ofbinders without limitation are silica, aluminas, silica-alumina,magnesia, zirconium and mixtures thereof. A preferred binder material isalumina, with eta- and/or especially gamma-alumina being favored.Usually the composite and optional binder are mixed along with apeptizing agent such as HCl, HNO₃, KOH, etc. to form a homogeneousmixture which is formed into a desired shape by forming means well knownin the art. These forming means include extrusion, spray drying, oildropping, marumarizing, conical screw mixing, etc. Extrusion meansinclude screw extruders and extrusion presses. The forming means willdetermine how much water, if any, is added to the mixture. Thus, ifextrusion is used, then the mixture should be in the form of a dough,whereas if spray drying or oil dropping is used, then enough water needsto be present in order to form a slurry. These particles are calcined ata temperature of about 260° C. to about 650° C. for a period of about0.5 to about 2 hours.

[0034] The catalytic composites of the present invention either assynthesized or after calcination can be used as catalysts in hydrocarbonconversion processes. Calcination is required, for example, to formzirconium oxide from zirconium hydroxide. Hydrocarbon conversionprocesses are well known in the art and include cracking, hydrocracking,alkylation of both aromatics and isoparaffins, isomerization,polymerization, reforming, dewaxing, hydrogenation, dehydrogenation,transalkylation, dealkylation, hydration, dehydration, hydrotreating,hydrodenitrogenation, hydrodesulfurization, methanation, ring opening,and syngas shift processes. Specific reaction conditions and the typesof feeds, which can be used in these processes, are set forth in U.S.Pat. Nos. 4,310,440 and 4,440,871, which are hereby incorporated byreference. A preferred hydrocarbon conversion process is theisomerization of paraffins.

[0035] In a paraffin isomerization process, common naphtha feedstocksboiling within the gasoline range contain paraffins, naphthenes, andaromatics, and may comprise small amounts of olefins. Feedstocks whichmay be utilized include straight-run naphthas, natural gasoline,synthetic naphthas, thermal gasoline, catalytically cracked gasoline,partially reformed naphthas or raffinates from extraction of aromatics.The feedstock essentially is encompassed by the range of a full-rangenaphtha, or within the boiling point range of 0° C. to 230° C.

[0036] The principal components of the preferred feedstock are alkanesand cycloalkanes having from 4 to 10 carbon atoms per molecule,especially those having from 7 to 8 carbon atoms per molecule. Smalleramounts of aromatic and olefinic hydrocarbons also may be present.Usually, the concentration of C₇ and heavier components is more thanabout 10 mass-% of the feedstock. Although there are no specific limitsto the total content in the feedstock of cyclic hydrocarbons, thefeedstock generally contains between about 2 and 40 mass-% of cyclicscomprising naphthenes and aromatics. The aromatics contained in thenaphtha feedstock, although generally amounting to less than the alkanesand cycloalkanes, may comprise from 0 to 20 mass-% and more usually from0 to 10 mass-% of the total. Benzene usually comprises the principalaromatics constituent of the preferred feedstock, optionally along withsmaller amounts of toluene and higher-boiling aromatics within theboiling ranges described above.

[0037] Contacting within the isomerization zones may be effected usingthe catalyst in a fixed-bed system, a moving-bed system, a fluidized-bedsystem, or in a batch-type operation. A fixed-bed system is preferred.The reactants may be contacted with the bed of catalyst particles ineither upward, downward, or radial-flow fashion. The reactants may be inthe liquid phase, a mixed liquid-vapor phase, or a vapor phase whencontacted with the catalyst particles, with excellent results beingobtained by application of the present invention to a primarilyliquid-phase operation. The isomerization zone may be in a singlereactor or in two or more separate reactors with suitable meanstherebetween to ensure that the desired isomerization temperature ismaintained at the entrance to each zone. Two or more reactors insequence are preferred to enable improved isomerization through controlof individual reactor temperatures and for partial catalyst replacementwithout a process shutdown.

[0038] Isomerization conditions in the isomerization zone includereactor temperatures usually ranging from about 25° C. to 300° C. Lowerreaction temperatures are generally preferred in order to favorequilibrium mixtures having the highest concentration of high-octanehighly branched isoalkanes and to minimize cracking of the feed tolighter hydrocarbons. Temperatures in the range of about 100° C. toabout 250° C. are preferred in the process of the present invention.Reactor operating pressures generally range from about 100 kPa to 10 Mpaabsolute, preferably between about 0.3 and 4 Mpa. Liquid hourly spacevelocities range from about 0.2 to about 25 hr⁻¹, with a range of about0.5 to 10 hr⁻¹ being preferred.

[0039] Hydrogen is admixed with or remains with the paraffinic feedstockto the isomerization zone to provide a mole ratio of hydrogen tohydrocarbon feed of from about 0.01 to 20, preferably from about 0.05 to5. The hydrogen may be supplied totally from outside the process orsupplemented by hydrogen recycled to the feed after separation from thereactor effluent. Light hydrocarbons and small amounts of inert materialsuch as nitrogen and argon may be present in the hydrogen. Water shouldbe removed from hydrogen supplied from outside the process, preferablyby an adsorption system as is known in the art. In a preferredembodiment, the hydrogen to hydrocarbon mole ratio in the reactoreffluent is equal to or less than 0.05, generally obviating the need torecycle hydrogen from the reactor effluent to the feed.

[0040] Upon contact with the catalyst, at least a portion of theparaffinic feedstock is converted to desired, higher octane, isoparaffinproducts. The catalyst of the present invention provides the advantagesof high activity and improved stability.

[0041] The isomerization zone generally also contains a separationsection, optimally comprising one or more fractional distillationcolumns having associated appurtenances and separating lightercomponents from an isoparaffin-rich product. Optionally, a fractionatormay separate an isoparaffin concentrate from a cyclics concentrate withthe latter being recycled to a ring-cleavage zone.

[0042] Preferably part or all of the isoparaffin-rich product and/or theisoparaffin concentrate are blended into finished gasoline along withother gasoline components from refinery processing including, but notlimited to, one or more of butanes, butenes, pentanes, naphtha,catalytic reformate, isomerate, alkylate, polymer, aromatic extract,heavy aromatics, gasoline from catalytic cracking, hydrocracking,thermal cracking, thermal reforming, steam pyrolysis and coking,oxygenates such as methanol, ethanol, propanol, isopropanol, tert-butylalcohol, sec-butyl alcohol, methyl tertiary butyl ether, ethyl tertiarybutyl ether, methyl tertiary amyl ether and higher alcohols and ethers,and small amounts of additives to promote gasoline stability anduniformity, avoid corrosion and weather problems, maintain a cleanengine and improve driveability.

[0043] The following examples serve to illustrate certain specificembodiments of the present invention. These examples should not,however, be construed as limiting the scope of the invention as setforth in the claims. There are many possible other variations, as thoseof ordinary skill in the art will recognize, which are within the scopeof the invention.

EXAMPLE 1

[0044] Catalyst samples of Tables 1, 2, and 3 were prepared startingwith zirconium hydroxide that had been prepared by precipitatingzirconyl nitrate with ammonium hydroxide at 65° C. The zirconiumhydroxide was dried at 120° C., ground to 40-60 mesh. Multiple discreteportions of the zirconium hydroxide were prepared. Solutions of eitherammonium metatungstate or a metal salt (component 1) were prepared andadded to the portions of zirconium hydroxide. The materials wereagitated briefly and then dried with 80° C. to 100° C. air whilerotating. The impregnated samples were then dried in a muffle oven at150° C. for 2 hours under air. Solutions of a metal salt (component 2,where component 2 is not the same as component 1) were prepared andadded to the dried materials. The samples were briefly agitated anddried while rotating. The samples were then calcined at 600° C. to 850°C. for 5 hours. The final impregnation solutions of chloroplatinic acidwere prepared and added to the solids. The samples were agitated anddried while rotating as before. The samples were finally calcined at525° C. in air for 2 hours. In Table 1 below, it can be seen that thecatalysts were made at silicon or phosphorous modifier levels of 0.25mass-%, 0.5 mass-%, 0.75 mass-%, 1 mass-%, and 1.5 mass-%; tungstatelevels of 10 mass-%, 15 mass-%, 20 mass-%, and 25 mass-%; andcalcination temperatures of 600° C., 700° C., and 800° C. The catalystsalso contained 0.4 mass-% platinum. Table 1 represents a total of 120different catalysts that were made.

[0045] In Table 2 below, it can be seen that the catalysts were made atphosphorus modifier levels of 0.025 mass-%, 0.05 mass-%, and 0.1 mass-%;tungstate levels of 20 mass-%, 22.5 mass-%, 25 mass-%, and 30 mass-%;and calcination temperatures of 700° C., 800° C., and 850° C. Thecatalysts also contained 0.4 mass-% platinum. Table 1 represents a totalof 28 different catalysts that were made.

[0046] In Table 3 below, it can be seen that the catalysts were made atgermanium modifier levels of 0.5 mass-%, 1 mass-%, and 2.5 mass-%;tungstate levels of 10 mass-%, 15 mass-%, and 20 mass-%; and calcinationtemperatures of 600° C., 700° C., and 800° C. The catalysts alsocontained 0.4 mass-% platinum. Table 3 represents a total of 27different catalysts that were made. TABLE 1 Si (mass %) 0.25 0.25 0.250.25 0.5 0.5 0.5 0.5 0.75 0.75 0.75 0.75 W (mass %) 10 15 20 25 10 15 2025 10 15 20 25 Calc. Temp ° C. 600 600 600 600 600 600 600 600 600 600600 600 Si (mass %) 0.25 0.25 0.25 0.25 0.5 0.5 0.5 0.5 0.75 0.75 0.750.75 W (mass %) 10 15 20 25 15 25 10 20 10 25 20 15 Calc. Temp ° C. 700700 700 700 700 700 700 700 700 700 700 700 Si (mass %) 0.25 0.25 0.250.25 0.5 0.5 0.5 0.5 0.75 0.75 0.75 0.75 W (mass %) 10 15 20 25 15 25 1020 10 25 20 15 Calc. Temp ° C. 800 800 800 800 800 800 800 800 800 800800 800 P (mass %) 0.25 0.25 0.25 0.25 0.5 0.5 0.5 0.5 0.75 0.75 0.750.75 W (mass %) 10 15 20 25 10 15 20 25 10 15 20 25 Calc. Temp ° C. 600600 600 600 600 600 600 600 600 600 600 600 P (mass %) 0.25 0.25 0.250.25 0.5 0.5 0.5 0.5 0.75 0.75 0.75 0.75 W (mass %) 10 15 20 25 15 25 1020 10 25 20 15 Calc. Temp ° C. 700 700 700 700 700 700 700 700 700 700700 700 P (mass %) 0.25 0.25 0.25 0.25 0.5 0.5 0.5 0.5 0.75 0.75 0.750.75 W (mass %) 10 15 20 25 15 25 10 20 10 25 20 15 Calc. Temp ° C. 800800 800 800 800 800 800 800 800 800 800 800 Si (mass %) 1 1 1 1 1.5 1.51.5 1.5 W (mass %) 10 15 20 25 10 15 20 25 Calc. Temp ° C. 600 600 600600 600 600 600 600 Si (mass %) 1 1 1 1 1.5 1.5 1.5 1.5 W (mass %) 15 2010 25 15 20 25 10 Calc. Temp ° C. 700 700 700 700 700 700 700 700 Si(mass %) 1 1 1 1 1.5 1.5 1.5 1.5 W (mass %) 15 20 10 25 15 20 25 10Calc. Temp ° C. 800 800 800 800 800 800 800 800 P (mass %) 1 1 1 1 1.51.5 1.5 1.5 W (mass %) 10 15 20 25 10 15 20 25 Calc. Temp ° C. 600 600600 600 600 600 600 600 P (mass %) 1 1 1 1 1.5 1.5 1.5 1.5 W (mass %) 1520 10 25 15 20 25 10 Calc. Temp ° C. 700 700 700 700 700 700 700 700 P(mass %) 1 1 1 1 1.5 1.5 1.5 1.5 W (mass %) 15 20 10 25 15 20 25 10Calc. Temp ° C. 800 800 800 800 800 800 800 800

[0047] TABLE 2 P (mass %) 0.025 0.05 0.05 0.05 0.1 0.1 0.1 W (mass %)22.5 20 25 30 20 25 30 Calc. Temp ° C. 700 700 700 700 700 700 700 P(mass %) 0.025 0.05 0.05 0.05 0.1 0.1 0.1 W (mass %) 22.5 20 25 30 20 2530 Calc. Temp ° C. 800 800 800 800 800 800 800 P (mass %) 0.025 0.050.05 0.05 0.1 0.1 0.1 0.25 0.25 0.25 1 1 1 W (mass %) 22.5 20 25 30 2025 30 20 25 30 20 25 30 Calc. Temp ° C. 850 850 850 850 850 850 850 850850 850 850 850 850

[0048] TABLE 3 Ge 0.5 0.5 0.5 1 1 1 2.5 2.5 2.5 W 10 15 20 10 15 20 1015 20 Calc. Temp ° C. 600 600 600 600 600 600 600 600 600 Ge 0.5 0.5 0.51 1 1 2.5 2.5 2.5 W 10 15 20 10 15 20 10 15 20 Calc. Temp ° C. 700 700700 700 700 700 700 700 700 Ge 0.5 0.5 0.5 1 1 1 2.5 2.5 2.5 W 10 15 2010 15 20 10 15 20 Calc. Temp ° C. 800 800 800 800 800 800 800 800 800

EXAMPLE 2

[0049] The catalysts of Example 1 were prepared as described above inExample 1. Also, reference catalysts were prepared as described inExample 1 but with the addition of the modifier step being omitted fromthe preparation. Approximately 95 mg of each sample was loaded into amulti-unit reactor assay. The catalysts were pretreated in air at 450°C. for 6 hours and reduced at 200° C. in H₂ for 1 hour. n-Heptane, 8mol-%, in hydrogen was then passed over the samples at 120° C., 150° C.,and 180° C., approximately 1 atm, and 0.3, 0.6, and 1.2 hr⁻¹ WHSV (basedon heptane only). The products were analyzed using online gaschromatographs.

[0050] To exemplify the data, selected results are shown in FIGS. 1-4for experiments at 180° C., 0.6 hf⁻¹ WHSV, and using catalystscomprising 10, 20 and 25 mass-% W, and 0.4 mass-% Pt. The identity ofthe modifier (or first component), the amount of modifier, the amount oftungstate, and the calcination temperature are identified along thex-axis of the plots of FIGS. 1-4. Data where the identity of themodifier is listed as “none”, corresponds to a reference catalystcontaining no modifier. FIG. 1 is a plot of the conversion of heptaneachieved by each of the selected catalysts. All of the catalystsindicate activity, with silicon-modified catalysts showing greaterconversion than the phosphorus-modified catalysts. However, at lowphosphorus levels, activity still trends upward at high levels oftungstate and high calcination temperatures. The optimum tungstateamount appears to be in the range of about 20 to about 25 mass-%. Anumber of the catalysts of the present invention however, exhibitgreater conversion with a calcination at 800° C. than at either 750° C.or 850° C. Therefore, a preferred calcination temperature is at 800° C.

[0051]FIG. 2 shows the selectivity of the catalysts for C₇isomerization. This plot demonstrates that even though some cracking isoccurring, selectivities to C₇ isomerization remain high. FIG. 3 showsthe selectivity of the catalysts for C₇ isomerization to produce two ofthe desired dimethyl-branched isomers, 2,2-dimethylpentane and2,4-dimethylpentane. Again, the data demonstrates that silicon-modifiedcatalysts show superior results and silicon is therefore a preferredmodifier over phosphorus. FIG. 4 shows the yield of the catalysts for C₇isomerization to produce two desired dimethyl-branched isomers,2,2-dimethylpentane and 2,4-dimethylpentane.

[0052] The data discussed above indicates a particular preference forsilicon as a modifier over phosphorus. Therefore, FIGS. 5-8 presentfurther selected results of the experiment where silicon was themodifier. On each of FIGS. 5-8, the amount of tungsten on the catalyst,the amount of modifier on the catalyst, the calcination temperature ofthe catalyst, and the weight hourly space velocity of the run is foundon the x-axis. In FIG. 5, the y-axis is the conversion of the n-heptanefeed. The plot demonstrates that conversion increases as the amount oftungsten increases, but conversion decreases as the weight hourly spacevelocity increases. However, with other variables remaining constant,increasing the amount of modifier from 0.25 mass-% to 1.5 mass-% doesnot have a dramatic effect on the conversion. FIG. 6 demonstrates thatthe selectivity for C₇ isomerization increases with increasing spacevelocity. However, FIG. 7 shows that the opposite is true whenconsidering the selectivity to two of the desired dimethyl-branchedisomers, 2,2-dimethylpentane and 2,4-dimethylpentane. FIG. 8 shows theyield of two of the desired dimethyl-branched isomers,2,2-dimethylpentane and 2,4-dimethylpentane. In general, the results inFIG. 8 indicate that the yield to the specific dimethylpentane isomers(1) decreases as the space velocity is increased; (2) is highest with acalcination temperature of 800° C.; and (3) is greater at the lowerlevels of modifiers.

What is claimed is:
 1. A process for converting hydrocarbons bycontacting a feed with a solid acid catalyst to generate a convertedproduct, the catalyst comprising a support comprising a tungstated oxideor hydroxide of at least an element of Group IVB (IUPAC 4) of thePeriodic Table, a first component selected from the group consisting ofat least one Group IVA (IUPAC 14) component, at least one Group VA(IUPAC 15) component, and mixtures thereof, and a second componentselected from the group consisting of platinum-group metals and mixturesthereof.
 2. The process of claim 1 wherein the hydrocarbon conversionprocess is selected from the group consisting of cracking,hydrocracking, aromatic alkylation, isoparaffin alkylation,isomerization, polymerization, reforming, dewaxing, hydrogenation,dehydrogenation, transalkylation, dealkylation, hydration, dehydration,hydrotreating, hydrodenitrogenation, hydrodesulfurization, methanation,ring opening, and syngas shift.
 3. A process for the isomerization of aparaffinic feedstock to obtain a product having an increased isoparaffincontent comprising contacting the paraffinic feedstock in anisomerization zone maintained at isomerization conditions comprising atemperature from about 25° C. to about 300° C., a pressure from about100 kPa to about 10 Mpa and liquid hourly space velocity from about 0.2to about 15 hr⁻1 with a solid acid isomerization catalyst, comprising atungstated oxide or hydroxide of elements of Group IVB (IUPAC 4) of thePeriodic Table, a first component selected from the group consisting ofat least one Group WVA (IUPAC 14) component, at least one Group VA(IUPAC 15) component, and mixtures thereof, and a second componentselected from the group of platinum-group metals and mixtures thereof,and recovering an isoparaffin-rich product.
 4. The process of claim 3wherein free hydrogen is present in the isomerization zone in an amountfrom about 0.01 to about 20 moles per mole of C₅+ hydrocarbons presentin the zone.
 5. The process of claim 3 wherein the isomerizationconditions comprise a temperature from about 100° C. to about 250° C., apressure from about 300 kPa to about 4 mPa, and a liquid hourly spacevelocity from about 0.5 to about 15 hr⁻¹, and wherein free hydrogen ispresent in the isomerization zone in an amount from about 0.01 to about20 moles per mole of C₅+ hydrocarbons present in the zone.
 6. Theprocess of claim 3 wherein the isomerization catalyst further comprisesa refractory inorganic-oxide binder.
 7. The process of claim 6 whereinthe refractory inorganic-oxide binder comprises alumina.
 8. The processof claim 3 wherein the first component is selected from the groupconsisting of silicon, phosphorus or mixtures thereof and the secondcomponent is platinum.
 9. The process of claim 3 wherein the catalystfurther comprises a third component selected from the group consistingof iron, cobalt, nickel, rhenium, and mixtures thereof.
 10. The processof claim 9 wherein the third component is iron in an amount from about 1to about 5 mass-%.
 11. The process of claim 3 further comprising usingat least a portion of the isoparaffin-rich product to blend a gasolineproduct.